If you'd like, you can sear the chuck roast on each side to brown - or you can just put it in the crockpot un-seared. I prefer to sear mine first, but it's optional.
Place the roast in your crockpot. Mix together the beef broth & Italian salad dressing mix with a fork. Pour over the roast. Pour the jar of pepperoncini peppers (and juice!) over top. Add the garlic if you're using it. Put the lid on your slowcooker & cook on low for 6-8 hours. Shred with 2 forks & return to the crockpot with the juices.
Serve. I like mine on sandwich buns (with melted provolone cheese!) served alongside a cup of the au jus from the crockpot to dip my sandwich in. It's also delicious served by itself, or on rice, noodles - or inside a tortilla or pita bread.